Formation of solvate structures by the ortho-, meta-, and para-isomers of hydroxybenzoic acid in supercritical fluid


Cite item

Full Text

Open Access Open Access
Restricted Access Access granted
Restricted Access Subscription Access

Abstract

The solvate structures formed by the ortho-, meta-, and para-isomers of hydroxybenzoic acid (o-HBA, m-HBA, and p-HBA) with a polar co-solvent (methanol at a concentration of 0.030 and 0.035 mole fractions) in supercritical carbon dioxide at a constant density of 0.7 g/cm3 and temperatures of 318 and 328 K have been studied by the classic molecular dynamics. It has been determined that a stable hydrogen-bonded complex with the co-solvent forms via the hydrogen of the carboxyl group for all isomers. The probability of this complex existence is high at all temperatures and concentrations. In the o-HBA molecule, the other functional groups are engaged in the intramolecular hydrogen bond, but not involved in interactions with methanol. It has been found that m-HBA and p-HBA can be involved in hydrogen bonds with methanol via hydroxyl hydrogen and oxygen atoms; they are characterized by the presence of one more co-solvent molecule (rarely, two molecules) in their solvation shell and intermittent formations/breakages of hydrogen bonds via other functional groups. These bonds are far less stable, and their formation is sensitive to change of temperature and co-solvent concentration. It has been concluded that the degree of selective solvation of m-HBA and p-HBA by co-solvent molecules is approximately the same, but the rate of structural rearrangements in the nearest environment of m-HBA is higher than that of p-HBA.

About the authors

M. L. Antipova

Krestov Institute of Solution Chemistry

Email: vep@isc-ras.ru
Russian Federation, Ivanovo

D. L. Gurina

Krestov Institute of Solution Chemistry

Email: vep@isc-ras.ru
Russian Federation, Ivanovo

E. G. Odintsova

Krestov Institute of Solution Chemistry

Email: vep@isc-ras.ru
Russian Federation, Ivanovo

V. E. Petrenko

Krestov Institute of Solution Chemistry

Author for correspondence.
Email: vep@isc-ras.ru
Russian Federation, Ivanovo

Supplementary files

Supplementary Files
Action
1. JATS XML

Copyright (c) 2017 Pleiades Publishing, Ltd.